1. Field of the Invention
The invention is applicable to the non-destructive testing of metal pieces, and more particularly to the ultrasonic checking thereof by immersion in a coupling liquid such as water.
The document FR-A-2650144 discloses an ultrasonic method for testing, by immersion, a metal piece using at least one transducer which emits ultrasonic waves into the piece. That document discloses the use of a transducer which focuses at a point inside the piece, the points of the emitting surface of that transducer being equidistant acoustically from the internal point.
Usually, the "focusing point" or focus of a transducer of this kind is surrounded by an acoustic volume comprising a focal spot which extends along the axis of propagation of the ultra-sound, and the geometry and acoustic structure of the focal spot make difficult and uncertain the ultrasonic testing of pieces such as thick bars made of titanium alloys intended for the manufacture of finished pieces or elements for use in aeronautics, the testing having to satisfy high quality requirements.
The inventor has sought ways of solving the corresponding problems, and of improving the reproducibility and accuracy of such ultrasonic testing by immersion.